The present invention generally relates to an assembling position-adjusting mechanism of a spindle motor for a magnetic disk apparatus, and more particularly to an assembling position-adjusting mechanism of a spindle motor for a magnetic disk apparatus which mechanism is advantageously used for adjusting a position of a spindle motor with respect to a magnetic head during assembling process.
FIG. 1 is a perspective view showing an entire part of a magnetic disk apparatus 1 (hereinafter called apparatus 1) for 3.5-inch disks which apparatus is related to the present invention. A magnetic head 2, a head carriage 3 that supports and moves the magnetic head 2, and a spindle motor 4 that clamps and rotates a magnetic disk are assembled in the apparatus 1.
Generally, in a magnetic disk apparatus for 3.5-inch disks, since a high accuracy is required for a positional relationship between a magnetic head and tracks formed on a magnetic disk, a mechanism is needed for adjusting the positional relationship during an assembling process.
FIG. 2 shows a positional relationship between the magnetic head 2 and a track 6 formed on the magnetic disk loaded on the spindle motor 4 of FIG. 1. The magnetic head 2 overlaps over the entire width of the track 6 and the center line of the magnetic head 2 (a line perpendicular to the length of the magnetic head 2, as shown in FIG. 2) is positioned at an angle .theta. from a radius line 7 of the magnetic disk (i.e. radius line of the spindle motor 4).
In order to adjust this positional relationship, three kinds of position adjustments are needed. That are azimuth alignment adjustments for an angle of a head gap on the magnetic head 2 with respect to the track (adjustment of .theta. of FIG. 2), radial alignment adjustments for a position of the magnetic head 2 in a radial direction (adjustment in a direction indicated by an arrow Y of FIG. 2), and index adjustments for a position of the magnetic head 2 with respect to an index-pulse position (adjustment in a direction indicated by an arrow X of FIG. 2).
Firstly, a description will be given of the azimuth alignment with reference to FIG. 3. FIG. 3 is a plan view of a conventional azimuth adjusting mechanism. The head carriage 3, on which the magnetic head 2 is mounted, is slidably supported by a guide rod 8, and one end of the head carriage 3 is engaged with a lead screw 10 extending from a stepping motor 11 so that the head carriage 3b moves along the guide rod 8 by rotation of the lead screw 10.
In the azimuth adjusting mechanism in the figure, the azimuth of the magnetic head 2 is adjusted by inclining the head carriage 3 (for example as shown by a chain line in FIG. 3) from the center line 7 of the spindle motor not shown in the figure. This can be done by displacing a movable end 8a of the guide rod 8 about a fixed end 8b of the guide rod 8b in a direction indicated by an arrow A of FIG. 3 by screwing a taper screw 9.
The radial alignment adjustment is performed by adjusting a mounting angle of the stepping motor 11 in a rotational direction of the lead screw 10. The magnetic head 2 moves in the radial direction of the spindle motor in accordance with a rotation of the lead screw formed on the rotational shaft of the stepping motor 11. The stopping position of the magnetic head 2 is determined by the stopping position of the lead screw 10 in the rotational direction. Thus, the stopping position of the head carriage 2 in the radial direction is adjusted by adjusting the mounting position of the stepping motor 11, which results in adjusting the position of the lead screw 10 in the rotational direction thereof.
Conventionally, the index adjustment is performed by adjusting an index-pulse generating means inside the spindle motor. Namely, a positional relationship between the magnetic head 2 and the index pulse generating point is adjusted by shifting a generating time of an index pulse.
However, in the above mentioned azimuth adjustment mechanism, a space for providing the taper screw 9 is limited. Additionally, since the guide rod 8 is thin, there is a problem in that the guide rod 8 bends when a large displacement is effected to the guide shaft 8. Further, when a tolerance of parts comprising a head carriage driving mechanism goes to the worst condition, there is a risk that the flap 12 makes contact with the photo-interrupter provided for detecting the track 00 of the magnetic disk.
Additionally, the radial alignment adjustment and the index adjustment must be performed separately; this results in time- and labor-consuming adjustments.